A variety of crosslinking reagents with a maleimide group are widely used for crosslinking proteins to proteins, or proteins to other biomolecules. A key challenge in maleimide crosslinking technology has been the quantitation of maleimide linked to a single protein or antibody. Maleimides can be directly assayed spectrophotometrically at 302 nm. However, the small extinction coefficient of 620 M-1cm-1 renders this assay insensitive, and the assay is further complicated by the protein absorbance at the same wavelength. AAT Bioquest's Amplite® Rapid Colorimetric Maleimide Quantitation Kit provides a rapid and accurate method to quantify maleimide using our proprietary maleimide sensor Maleimide Blue™ with the maximum absorbance at ~780nm. The principle of this assay is that Maleimide Blue™ reacts with the maleimide-linked sample, and the resulted product is run through a single spin column to remove the excess sensor. The absorption spec